Various display devices have been suggested to display an image. These display devices adopt a luminance sensor in order to control light emitting brightness by measuring surrounding luminance. Additionally, provided is a display device in which an additional touch screen panel capable of detecting a contact position of a user to perform a touch panel function is mounted on a display panel. However, because an additional touch screen panel is required to be mounted in order to realize a touch panel, there is a disadvantage which increases the thickness of a display device.